Introduction - YASKAWA SGD7S series Product Manual

3.1 Introduction

3.1 Introduction
You can use less-deviation control to reduce the deviation during movement and increase the
locus tracking performance.
The FT19 SERVOPACKs are used for applications that require reference tracking performance
during movement, including the decrease of tracking error and the prevention of interference
between the equipment and moving parts, which can be caused by the influences of position
response delay.
Position deviation
Position reference
Less-deviation control is enabled or disabled with Pn190 = n.
• Pn190 = n.
• Pn190 = n.
Adjusting less-deviation control depends on the less-deviation control mode that you use.
• Less-Deviation Control 1 (Pn195 = n.0
• Less-Deviation Control 2 (Pn195 = n.2
An outline of the control block diagram for Less-Deviation Control 2 is given below.
· Analog Voltage/Pulse Train
Input
reference
· MECHATROLINK-III
*1.
These parameters are used for adjustments for Rotary Servomotors.
*2.
These parameters are used for adjustments for Linear Servomotors.
Important
Important
3-2
Less-Deviation Control Not Used
speed
0 100 200 300
Time (ms)

1: Use less-deviation control.

0: Do not use less-deviation control.
Position Reference Filter
References: Pn216 and Pn217
+
Communications References:
Pn811 and Pn812
If you use less-deviation control under any of the following conditions, vibration, noise, or over-
shooting may occur.
• Condition 1: The machine has low rigidity. (Guideline: There is a large resonance point in the
frequency band from 300 Hz and lower.)
• Condition 2: The machine has large variations in the load.
• Condition 3: The resolution of the encoder is low.
If the condition 1 or 2 is met, do not use less-deviation control.
If the condition 3 is met, we recommend using a motor with an encoder that has a resolution of
20 bits or higher.
Also, for fully-closed loop control, we recommend using a linear scale (external encoder) that has
a resolution equivalent to the motor encoder.
The optimum feedforward is set inside the SERVOPACK for less-deviation control. A speed feed-
forward input or torque feedforward input from the host controller is normally not used at the
same time as less-deviation control. However, they can be used together with less-deviation con-
trol if necessary. If they are used together and an inappropriate feedforward value is input, over-
shooting may occur.
Position deviation
Position reference
400 500

): Pn193 and Pn191

): Custom Tuning on the SigmaWin+
Torque/Force Feedforward
Pn197, Pn198, Pn199, Pn19B *1 , Pn19D
Speed Feedforward
Pn196
+
Position Control
+
− −
Pn102,
Pn11F,
Pn19A
Less-Deviation Control Used
The position deviation
during operation is
essentially 0.
speed
0 100 200 300
Time (ms)

X.
*2
Friction
Speed Control
Compensation
+
+
Pn100, Pn101,
Pn121,
Pn401
Pn123
400 500
Controlled object
Motor Mechanism